The traditional approach for cooling turbine blades and nozzles is to extract high pressure cooling air from a source, for example, by s extracting air from the intermediate and last stages of the turbine compressor. External piping is used to supply air to the nozzles with air film cooling typically being used, the air exiting into the hot gas stream of the turbine. In advanced gas turbine designs, it has been recognized that the temperature of the hot gas flowing past the turbine components could be higher than the melting temperature of the metal. It is therefore necessary to establish a cooling scheme to protect the hot gas path components during operation. Steam supplied in a closed circuit to cool gas turbine nozzles (stator vanes) has been demonstrated to be a preferred cooling medium, particularly for combined cycle plants. See, for example, U.S. Pat. No. 5,253,976, of common assignee herewith. Because steam has a higher heat capacity than the combustion gas, it is inefficient to allow the coolant steam to mix with the hot gas stream. Consequently, it is desirable to maintain cooling steam inside the hot gas path components in a closed circuit. It has been found, however, that certain areas of the components of the hot gas path cannot practically be cooled with steam in a closed circuit. For example, the relatively thin structure of the trailing edges of the nozzle vanes effectively precludes steam cooling of those edges.